*{
    margin:0;
    padding:0;
    box-sizing: border-box;
}
.yz{
    width: 700px;
    margin:auto;
}
.yz .nav>li{
    list-style: none;
    display: inline-block;
    cursor: pointer;
    padding:5px;
    position: relative;
}

.yz .nav>.active::after{
    content: "";
    border-bottom: 2px solid coral;
    position: absolute;
    width: 100%;
    left: 0;
    bottom: -1px;
}
.yz .main >div{
    display: none;
}
.yz .main>.active{
    display: block;
}
.main{
    font-size: 12px;
}